Ag-doped ZnO nanostructured thin films for transparent antibacterial surfaces: Effect of Ag content

This study explores the development of transparent antibacterial surfaces based on Ag-doped ZnO nanostructured thin films. The primary aim is to investigate the influence of silver (Ag) content on the optical transparency and antimicrobial properties of the films. ZnO, which is known for its inherent antibacterial properties and optical transparency, was doped with varying concentration of Ag (5, 10, 15, and 20 %) using the rapid thermal evaporation technique, followed by annealing to enhance film quality. The structural, optical, and antibacterial properties of the films were characterized using X-ray diffraction, field emission scanning electron microscopy, ultra-violet and visible UV-Vis spectroscopy, and microbial assays against Staphylococcus aureus (S. aureus). Results indicated that the incorporation of Ag nanoparticles improved significantly the antibacterial efficacy of ZnO films, and the bacterial inactivation was enhanced for high Ag concentrations especially at 15 % Ag. An increase in silver content modified the nanostructure, reduced optical transparency from 83 % to 56.5 %, and decreased the bandgap from 3.88 eV to 3.35 eV, followed by a rise to 3.69 eV at 20 % Ag. These changes were accompanied by the formation of silver agglomerates at higher doping levels. An optimal balance between preserving high optical transparency and attaining robust antibacterial efficacy was identified at intermediate Ag concentrations (10-15 %). This study highlights the potential of Ag-doped ZnO films as versatile coatings suitable for applications demanding both transparency and antimicrobial performance, including medical devices, display panels, and protective surfaces.